Vom utiliza formulele radicalilor dubli:
√a-√b=√a+c/2 - √a-c/2
√a+√b=√a+c/2 + √a-c/2
Unde c=√a²-b
√4-√7
a=4
b=7
c=√16-7=√9=3
√4-√7=√4+3/2 - √4-3/2=√7/√2-1/√2=√14/2-√2/2
√4+√7
a=4
b=7
c=√16-7=√9=3
√4+√7=√4+3/2 + √4-3/2=√7/√2 + 1/√2=√14/2+√2/2
x=√4-√7 + √4+√7=√14/2-√2/2 + √14/2+√2/2=2√14/2=√14
x=√14
x²=(√14)²=14
14 este numar natural.
